Este documento presenta las caracteristicas basicas de un lavador de gases tipo scrubber, sus componentes y algunas variables de diseño
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1-800-214-7716 www.midwestair.com
PO Box 5319 281 Hughes Drive Traverse City, MI 49686 Ph:231-941-5865 Fax: 231-941-1636
Mapco offers a complete line of quality built, cor-rosion- resistant horizontal and vertical fume scrub-bers. MAPCO FUME SCRUBBERS Mapco fume scrubber design is based on wetted, packed bed technology to achieve removal of water soluble contaminants, soluble gas and par-ticulate matter through Mass Transfer (gas absorp-tion) and Impingement (mechanical separation). • Gas Absorption - Noxious or otherwise undesir-
able gasses are absorbed into the liquid phase.
• Impingement - Particulate matter is removed
through impingement as it is first forced through a wetted packed bed and then through a chevron blade or mesh pad filter section.
Supplied in either counter-current flow (vertical) or cross-current flow (horizontal), these rugged units can be supplied with extended packed beds or in series. MW-100 Horizontal (cross flow) When horizontal installation is required, the MW-100 is preferred. This compact unit is ideal for mez-zanine or roof top mounting when a low profile is desired. Equipped with remote recirculation, the MW-100 is perfect for roof top mounting in cold climates. MW-200 Fan Scrubber (counter-current flow) The MW-200 is an economical, space saving unit equipped with built-in fan. The fan can be rotated 900 in (4) directions and eliminates the need for transitions and ductwork between the fan and scrubber. This unit is shipped in two pieces and is bolted together on site. MW-300 Vertical (counter-current flow) This design works well when floor space is at a pre-mium and is especially effective when greater bed depths or multiple-stage systems are required for gas absorption. The MW-300 can be equipped with a stack fan and also works well with a pedes-tal base fan mounted on the roof or mezzanine. OPERATING PRINCIPLES Contaminant removal is accomplished by first slowing the exhaust air to a velocity of less than 500 fpm. Scrubber liquor is recirculated from the self contained sump or remote tank and sprayed into a bed of corrosion-resistant, non-clogging, packing media. Depending on the application, the wetted pack surface provides a large area for
liquid/gas contact, allowing absorption of noxious gas and/or impingement of chemical mists. Once through the packed bed and prior to exiting the scrubber, the mist laden exhaust air must pass through a two stage gravity mist eliminator sec-tion. The first stage consists of a drop out area whereby the larger droplets fall out of the air stream. Secondly, the smaller mist particles are re-moved by an integral, vertically or horizontally mounted PVC chevron type mist eliminator provid-ing four 300 directional changes in air flow. Con-taminants are then carried away in the wash wa-ter via the overflow. Contaminants that are highly soluble in water usu-ally require less packing. Removal of contaminants which are low in solubility can be enhanced with the addition of a chemical scrubbing agent (pH or ORP system) and in some cases by installing a pre-filter at the exhaust hood or prior to the scrubber. RECIRCULATION RATES/ WATER CONSUMPTION Recirculation rates through Mapco fume scrub-bers are expressed in terms of GPM per cross-sectional area (ft2) of the scrubbing media. Opti-mal recirculation rates through your fume scrubber will be determined by Mapco application engi-neers, and will usually depend upon the removal efficiency desired, in conjunction with the bed depth and type of packing media. Gases with low solubility typically require higher liquid-to-gas ratios for optimal scrubbing efficiency within the packed bed. Applications primarily involving mist require much lower liquid-to-gas ratios. As scrubber liquor and exhaust air collide within the vessel, some of the recirculated water will be evaporated and carried off as gaseous H2O, especially in warm arid climates. Fresh water must be added to the scrub-ber sump to maintain the proper balance and liq-uid level. A float valve can be installed in the sump to make up for evaporation losses only. Most scrubbers are operated on a constant-overflow basis. A constant volume of fresh water is metered into the sump, and a constant effluent is pro-duced as the sump overflows through a fitting for this specific purpose. The constant overflow is nec-essary to keep chemical concentration as dilute as possible. The addition of an optional float valve, timer and actuated ball valve in conjunction with a pH con-trol system, allows for scheduled batch blow-down of the scrubber effluent, resulting in less water con-sumption and lower waste treatment costs. Alter-natively, the wet scrubber can be configured to blow-down a continuous low volume effluent to waste treatment, under pump pressure.
MAINTENANCE Experience has taught us that the best engineered systems can fail if they are not easily maintainable. With this in mind we have made every effort to include as a standard, the features that too often are overlooked or supplied as options on
comparable equipment. As a result, Mapco scrubbers require the least amount of maintenance of any competitive product available.
STANDARD FEATURES
• Corrosion-Resistant 3/8" Thick PVC
Shell Construction
• 2" X 3/4" Thick Inlet and Outlet Flanges
• Heavy Duty Coated Steel Channel
Base
• Flanged Spray Headers with Unions, Easily Removable for cleaning
• Packing Removal and Fill Doors
• Proprietary Chevron Mist Eliminator
Section
• Liquid Regulation Valves for Precision Adjustment
• Overflow and Drain
• Vertical, Sealless CPVC Pumps with
Run-Dry Capability • In-Line Strainer to Prevent Nozzle
• pH / ORP Control System • Automatic Batch Blowdown System • Common Base for Scrubber and Fan • Dual Mist Eliminators • Magnehelic or Photohelic Gauge • Inline Rotameters to indicate
recirculated flow
• Solenoid Valve - Fresh Water Make-up • Air or Liquid Flow Switch for Alarm • Fume ArrestorTM Mist Pre-filter • Polypropylene/FRP/SS Construction • Liquid Level Controls • Clear PVC Inlet Transition for Inspection
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Mapco scrubbers utilize water as the main scrubbing agent. In certain cases contaminants which are low in solubility require the addition of chemical additives to: 1. Neutralize contaminants in the fume scrubber. 2. Provide precise control over effluent quality and quantity. Mapco offers a pH control system to monitor and adjust the scrubbing liquor when necessary. This optional equipment can be incorporated into a new design as well as an existing installation.
Effluent Tank (Optional)
Chemical Feed Pump
CPVC Pump
Fresh Water Make − Up Flowmeter
PH Probe
PH Controller
110 Volt Supply
Scrubber Drain
Scrubber Supply
Recirculation Tank
(For Remote Applications)
In − Line Flowmeter
"Y" Strainer
Gate Valve
Ball Check
The addition of an optional float valve, timer and actuated ball valve, in conjunction with a pH control system, allows scheduled batch blow-down of the scrubber effluent resulting in less water consumption and lower waste treatment costs. The Mapco pH control system consists of : 1. Weather-tight, corrosion-resistant enclosure
containing a pH analyzer, terminal block and side wall mounted weather-proof electrical connections.
2. pH probe with cable 3. Chemical feed pump with check valve. As an
option, Mapco offers a corrosion-resistant reagent holding tank with necessary fittings for chemical feed pump connections.
DIMENSIONS [inches] Note: See page 10 for scrubber weights and transition lengths.
MW-100 Horizontal (cross flow) When horizontal installation is required, the MW-100 is preferred. This compact unit is ideal for mezzanine or roof top mounting and can be supplied with either self-contained or remote recirculation. The MW-100 is equipped with removable packing, chevron mist eliminator, fresh water make-up flow meter, strainer, CPVC pump and regulating valve.
DIMENSIONS [inches] Note: See page 10 for scrubber weights and transition lengths.
MW-200 Vertical (counter-current flow) with Blower The MW-200 is an economical, space saving unit equipped with built-in blower. The fan can be rotated 900 in four directions and eliminates the need for transitions and ductwork between the fan and scrubber. This unit is shipped in two pieces and is bolted together at the jobsite. The MW-200 is equipped with removable packing, mist eliminator, fresh water make-up flow meter, strainer, CPVC pump and regulating valve.
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F
H
D O.D.
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Steel Fan Support Legs (10,000 & 12,000 CFM Units Only)
MW-300 Vertical (counter-current flow) The MW-300 design works well when floor space is at a premium. This versatile scrubber is especially effective when greater bed depths or multiple stage scrubbers are required. The MW-300 is equipped with removable packing, mist eliminator, fresh water make-up flow meter, strainer, CPVC pump and regulating valve
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A
H
L 2"ø Drain & Overflow
F
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DIMENSIONS [INCHES] Note: See page 10 for scrubber weights and transition lengths.
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Drain
Scrubber Outlet Transition
Mesh Pad and Retainer
3/8" Mesh Pad Removal Door
Removable Spray Headers
Vertical CPVC Pump
Pack Fill Door
Pack Removal Door Overflow
Primed & Painted Structual Steel Base
Scrubber Inlet
3/8" Thick Scrubber Shell
Clear PVC Inspection Door
3/4" X 2" Flat Flanges and Reinforcing Strips
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Scrubber weights shown below are for scrubbers with two foot packed beds. For extended packed bed scrubbers add 4.2 lbs. per ft3 of packing. MW-200 and MW-300 scrubbers do not require additional weight for sump water. MW-100 scrubbers will require some calculation for additional weight due to extended sump. Calculate cubic feet of water based on a 10" liquid depth. Multiply ft3 of water by 62½ lbs. to find additional weight.
MW-100 HORIZONTAL MW-300 VERTICAL MW-200 FAN SCRUBBER
These efficiencies are intended as a guide only. Depending on the process, specific combinations and concentrations of fumes may result in substantially differ-ent values than depicted above. Consult your scrubber manufacturer for specific efficiencies. 1. Application of pH control results in lower water usage. 2. This application may require chemical addition, extended pack bed, once through water and high efficiency mist eliminator. 3. Depending on the process, wet scrubbing may not be necessary. Consider Mapco MW-400 horizontal mist eliminator, Mist Master in-line vertical or hori-
zontal mist eliminator, Terminator Exhaust hood or Enforcer III. 4. Depending on the process, inlet loading and temperature, a fine fog may be produced which is not included in the stated efficiencies. The addition of a
special high efficiency mist eliminator will be required to minimize fog. 5. Efficeincy is improved by chemical addition (other than pH control) . 6. Stated efficiency is for the combined nitric and phosphoric acid fumes. The efficiency for the NO2 portion of the fume is not listed. 7. Enforcer III on chromic acid in excess of 99.9% to 1.0 micron, Ultramact 99.9% to 99.9995 to 0.12 microns. NR = Not Recommended